全文获取类型
收费全文 | 37710篇 |
免费 | 6267篇 |
国内免费 | 1543篇 |
专业分类
电工技术 | 7137篇 |
技术理论 | 12篇 |
综合类 | 3955篇 |
化学工业 | 3526篇 |
金属工艺 | 824篇 |
机械仪表 | 2460篇 |
建筑科学 | 2852篇 |
矿业工程 | 643篇 |
能源动力 | 2187篇 |
轻工业 | 1360篇 |
水利工程 | 1392篇 |
石油天然气 | 1748篇 |
武器工业 | 270篇 |
无线电 | 4060篇 |
一般工业技术 | 1453篇 |
冶金工业 | 964篇 |
原子能技术 | 787篇 |
自动化技术 | 9890篇 |
出版年
2024年 | 47篇 |
2023年 | 252篇 |
2022年 | 619篇 |
2021年 | 730篇 |
2020年 | 782篇 |
2019年 | 871篇 |
2018年 | 916篇 |
2017年 | 856篇 |
2016年 | 1040篇 |
2015年 | 904篇 |
2014年 | 4562篇 |
2013年 | 3367篇 |
2012年 | 4313篇 |
2011年 | 5092篇 |
2010年 | 4314篇 |
2009年 | 3880篇 |
2008年 | 2041篇 |
2007年 | 1325篇 |
2006年 | 1354篇 |
2005年 | 1651篇 |
2004年 | 1346篇 |
2003年 | 939篇 |
2002年 | 650篇 |
2001年 | 586篇 |
2000年 | 510篇 |
1999年 | 456篇 |
1998年 | 395篇 |
1997年 | 296篇 |
1996年 | 311篇 |
1995年 | 246篇 |
1994年 | 218篇 |
1993年 | 186篇 |
1992年 | 129篇 |
1991年 | 87篇 |
1990年 | 52篇 |
1989年 | 40篇 |
1988年 | 42篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1959年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
31.
32.
面向应用的无线传感器网络 总被引:1,自引:0,他引:1
结合具体的应用环境分析了无线传感器网络发展到第二阶段需要考虑的重点问题;探讨了基于上述应用需求的无线传感器网络的协议栈结构和今后的研究方向。 相似文献
34.
35.
This paper addresses the problem of power control in a multihop wireless network supporting multicast traffic. We face the problem of forwarding packet traffic to multicast group members while meeting constraints on the signal-to-interference-plus-noise ratio (SINR) at the intended receivers. First, we present a distributed algorithm which, given the set of multicast senders and their corresponding receivers, provides an optimal solution when it exists, which minimizes the total transmit power. When no optimal solution can be found for the given set of multicast senders and receivers, we introduce a distributed, joint scheduling and power control algorithm which eliminates the weak connections and tries to maximize the number of successful multicast transmissions. The algorithm allows the other senders to solve the power control problem and minimize the total transmit power. We show that our distributed algorithm converges to the optimal solution when it exists, and performs close to centralized, heuristic algorithms that have been proposed to address the joint scheduling and power control problem. 相似文献
36.
Analysis of non-stationary electrochemical oscillations emerges utilization of the techniques allowing an observation of time evolution of their parameters such as instantaneous frequency, amplitude or frequency band. An algorithm of extraction of these parameters can be based on one of linear or quadratic time-frequency representations of oscillations record. In this paper, the authors present representatives of such transformations (Choi-Williams and Cone-shaped) originating from one of the most popular joint time-frequency energy distribution—Wigner-Ville distribution. Short introduction to the mathematics of the topic discussed is provided, then the authors present an example of application in the analysis of current oscillations of copper dissolution process. 相似文献
37.
38.
本文叙述了反应堆保护系统停棒与汽轮机降功率子系统的系统功能、保护参数和秦山核电站控制棒组插入监测器的设计与参数选择,确定了控制棒提升上极限值和在不同工况下棒插入低位、低-低位整定值,并在热态零功率条件下加以验证。试验证明参数选择是合理的,为功率运行阶段提供了数据。 相似文献
39.
Characteristics of hydrostatic bearing/seal parts for water hydraulic pumps and motors. Part 1: Experiment and theory 总被引:2,自引:0,他引:2
In this paper, the load-carrying capacity, power losses and stiffness of disk-type hydrostatic thrust bearings including the case of eccentric loading are discussed theoretically. The numerical analysis method is established based on a two-dimensional elastohydrostatic problem with an elastic deformation model, which is extended to adapt it for a non-axisymmetric load acting on the thrust bearing. The bearing is made of a combination of stainless steel/stainless steel and stainless steel/plastics. For the elastic materials, the maximum stiffness derived from, i.e., minimum film thickness is, larger than that of the rigid material in the range of a large ratio of pocket pressure and a hydrostatic balance ratio of over unity, which is defined as the ratio of the load to the maximum hydrostatic load-carrying capacity. The maximum load-carrying capacity and minimum power loss can exist in the domain of the hydrostatic balance ratio over unity for the case of the bearing consisting of elastic/rigid materials, in comparison with that composed of the same rigid materials. For the case of water, the power loss due to leakage flow is slightly larger but that due to frictional torque is much smaller than that in the case of hydraulic oil. Then, the total power loss is much smaller than that of hydraulic oil. 相似文献
40.